Modern inventory systems, such as those in materials handling facilities, distribution warehouses, mail-order warehouses, and custom-order manufacturing facilities, maintain a virtual inventory of items that are supposed to be housed at the facility. The virtual inventory may specify what items are supposed to be present, as well as a specific location within the facility where each item is supposed to be housed. In order to maintain accuracy, the virtual inventory should match a physical inventory of what items are actually housed at the facility, as well as the locations within the facility of where those items are actually housed.